A cross-tie is a generally rectangular item that is used to support the rails of railroad tracks. Cross-ties transfer the load of the railroad to the track ballast and subgrade and maintain the rails in the correct relative orientation and gauge. Cross-ties are typically comprised of wood, although they may be comprised of other materials, such as concrete, plastic, steel and others. Cross-ties also include plates that are positioned on the tie and are secured in place using railroad spikes. In typical applications, two plates will be secured to a cross-tie. Additional plates may be affixed to a cross-tie if needed. The two plates must be spaced apart by the distance between the two rails. The uniform distance between the plates, and consequentially the rails, is preferred. Railroad rails include a broad lower portion that fits within the railroad plate. Spikes are driven through the plate and include an offset head that secures the rail to the plate and to the cross-tie.
In some applications, particularly where a track is being repaired, cross-ties will be prepared at the work site immediately before they are used. In repairing track, it is often necessary to set each plate separately as the rail is laid into it. In other applications, particularly those involving new lines of railroad track, cross-ties can be prepared in a large quantity. They can be prepared either at the work site, or alternatively can be prepared at a distant location and transported to the site. The process of affixing plates to cross-ties before they are used on the railroad track is commonly referred to as pre-plating.
Wooden cross-ties are roughly cut and typically do not conform to uniform dimensions. Cross-ties are not rigorously sorted and therefore bundled with varying grades resulting in cross-ties with slightly different dimensions being pre-plated at the same time. The cross-ties are not exactly the same and the pre-plating process of cross-ties is complicated because the slight variations require different placement of the plates on the cross-ties. Although the cross-ties themselves can vary in dimensions, it is necessary for the plates to be accurately positioned. That is, it is necessary for the plates themselves to be parallel to one another and the distance between the plates to be uniform for each of the ties. It is preferable for each of the plates to be laterally centered on the cross-tie and the first plate positioned a set distance from the first end or line side. Because the cross-ties have varying widths and lengths the plates are not placed in the same exact position on the cross-tie. Slight variations in the cross-ties require slightly different placement of the plates. Although the plates are placed in slightly different locations on the cross-tie, it is still necessary that they remain separated by the appropriate distance and be substantially parallel.